FIELD OF THE INVENTION
The invention relates to a method of controlling inflation of an airbag in a motor-vehicle accident protection device, in which a gas generator is activated in response to a firing signal and inflates the airbag in dependence on operating conditions, a temperature of the gas generator is measured at least indirectly and the inflation takes place in dependence on the temperature. The invention also relates to a motor-vehicle airbag accident protection device, including an airbag, and an inflating device for the airbag having a gas generator, a firing device for activating the gas generator, a control device for controlling the operation of the inflating device in dependence on temperature, and a temperature-measuring device with a measuring sensor for at least indirectly sensing the temperature of the gas generator to generate a firing signal for the firing device.
Airbag protection devices or so-called airbags are becoming increasingly popular in motor vehicles. The mass flow of gas necessary for filling the airbag is currently usually produced by burning a solid fuel, for example sodium azide, wherein the fuel is ignited by a primer or detonating composition. Alternatively, gas generators which contain a solid propellant charge within a gas chamber are used, in which gas is stored in the gas chamber under high pressure (hybrid generators). When the propellant charge is ignited, which may likewise take place electrically through the use of a primer, a hole is produced at a predetermined location on the gas chamber and the airbag is inflated through that hole.
The pressure level of the airbag is a decisive variable for the restraining effect. If the pressure level is too low, there is the risk that, in spite of the airbag, a vehicle occupant may hit a steering wheel, for example, and suffer injuries. If, however, the pressure level is too high, that may lead to injuries to small people, children or infants. The pressure level which the airbag reaches is consequently a critical variable.
In addition, it has been found that, at low temperatures, in accidents with great deceleration and in the case of large, heavy vehicle occupants not wearing seat belts, there is the risk of the airbag pressure not being adequate to prevent the occupant from crashing through onto parts of the dashboard. At very high temperatures and in the case of small, lightweight vehicle occupants not wearing seat belts, on the other hand, there is the risk of the occupant being injured by the airbag during its deployment.
European Patent Application EP 0 790 157A2, corresponding to U.S. Pat. No. 5,664,802, discloses a motor-vehicle airbag accident protection device including an airbag, an inflating device for the airbag with a gas generator, a firing device for activating the gas generator and a control device for generating a firing signal for the firing device. A temperature-measuring device with a measuring sensor for sensing a temperature of the gas generator is also provided.